Corrosion of reinforcing steel in reinforced concrete structures (e.g., concrete parking garages, reinforced slabs on grade, concrete retaining walls, concrete buildings) is a pressing problem affecting hundreds of thousands of concrete structures such as concrete bridges. For example, the United States Federal Highway Administration has estimated that a relatively large portion (e.g., 15%) of the hundreds of thousands of bridges in the United States have been structurally compromised due to corrosion. The cost to repair or replace these highway bridges is estimated to be billions of dollars. Corrosion can be caused by, for example, chloride ions introduced to the surface of a concrete bridge deck when de-icing salts are applied to melt snow and remove ice from the area. The decision to, for example, repair or replace these concrete bridges depends largely on the corrosion state of the reinforcing bars installed within the concrete bridges and on assessments of the condition of the concrete cover over the reinforcement.
Using known techniques, assessing the condition of the concrete cover over reinforcing bars within concrete structures cannot be performed in a desirable fashion. For example, destructive, invasive methods can be used to physically examine the internal state of the concrete structure and measure the chloride content. However, these techniques may be undesirable in some situations because they require the destruction of portions of the structure. Known acoustic methods and ground penetrating radar methods can provide information about delamination and geometrical changes within the concrete, but these are generally late-stage corrosion indicators. Electrochemical methods, such as half-cell potential measurements and linear polarization, give information about the instantaneous probability and rate of reinforcement corrosion within the structure, but these known electrochemical methods do not provide direct information about the condition of the concrete cover. Concrete resistivity methods require precise conditions (e.g., precise solutions) and/or procedures to be performed with success and may not have desirable accuracy and/or coverage. In addition, some known instruments may only work in a laboratory setting where the reinforcing bars can be isolated from earth ground. In a field setting on, for example, a bridge deck, the electrical network of the bridge may be coupled to the earth ground, and, consequently, current monitoring using known instruments can yield questionable results. Thus, a need exists for systems, methods, and apparatus to address the shortfalls of present technology and to provide other new and innovative features.